1. Field of the Invention
This invention relates to a xeroradiographic material and a method of making same.
2. Description of the Prior Art
Recently, body-centered cubic (.gamma.-form) crystals of bismuth oxide-based compound oxides represented by the following general formula: EQU Bi.sub.x MO.sub.n
in which M designates at least one of germanium, silicon, titanium, gallium and aluminum, x denotes a number satisfying the condition 10.ltoreq.x.ltoreq.14, and n denotes a number of oxygen atoms stoichiometrically determined depending on M and X, have attracted attention for use as photoconductive substances. The .gamma.-form crystalline compound oxides become electrically conductive when exposed to X-rays. Therefore, it has been proposed in Japanese Unexamined Patent Publication No. 53(1978)-43531 to use them as photoconductive substances in xeroradiographic materials for forming electrostatic latent images by exposure to X-rays.
Xeroradiographic materials comprising a conductive substrate, and an X-ray sensitive layer formed of a dispersion containing the .gamma.-form crystal grains of the above-mentioned compound oxides in an organic binder and provided on the conductive substrate exhibit a remarkably high sensitivity to X-rays. For example, it is known to use a xeroradiographic material comprising a conductive substrate, and an amorphous selenium layer deposited on the conductive substrate for mammography and the like. In general, compared with the xeroradiographic material comprising an amorphous selenium layer, the xeroradiographic materials provided with an X-ray sensitive layer formed of a dispersion containing the .gamma.-form crystal grains of the above-mentioned compound oxides in an organic binder exhibit a sensitivity to X-rays about five to ten times higher.
When xeroradiographic materials are used for xeroradiography for the medical diagnostic purposes, it is desirable that the materials be as sensitive as possible to X-rays in order to minimize the exposure dose which patients receive. For this reason, it is desired to further increase the sensitivity of the xeroradiographic material comprising an X-ray sensitive layer formed of a dispersion containing the .gamma.-form crystal grains of the above-mentioned compound oxides in an organic binder.